Why does food only come in round cans?

[Zaskoda]

I rant about weird things... a lot.

So, canned food is usually in round cans. Square cans would make much better use of precious storage space.

I poked around. I found other folks with the same idea. I also found a patent on a canning process for square cans... but I wasn't able to actually find food in square cans.

Anyone else ever thought about this? I'm thinking about actually doing a little math to see how much space could be saved...

Hmm... maybe it's a marketable business idea? Meh... maybe not.

Edit: If they can make a square watermelon: http://www.hoax-slayer.com/images/square-watermelons-1.jpg

 

[James86004]

Spam comes in a rectangular can.

 

[Zaskoda]

Spam comes in a rectangular can.

And really, that's all you need to stock.

 

[MotoDave]

My guess is that originally round cans were a lot easier/cheaper to make, simply rolled from sheet metal and sealed with endcaps, where a square can would be more involved. Since they're now established I bet the change in manufacturing equipment to switch to square/rectangular cans would be cost prohibitive.

 

[Mr. Leary]

My guess is that originally round cans were a lot easier/cheaper to make, simply rolled from sheet metal and sealed with endcaps, where a square can would be more involved. Since they're now established I bet the change in manufacturing equipment to switch to square/rectangular cans would be cost prohibitive.

Bingo.

Square cans would also lack the uniform structural integrity of round cans... they cannot be stacked as high and still be resistant to denting on the sides. Its a logistics problem. It needs to be stacked either 4 or 8 feet high in a container. So without tertiary packaging to improve structure, damage would go up. Besides, with canned food, you will weigh out before you cube out, so the emphasis is on strength, not on maximizing useable volume.

 

[Zaskoda]

you will weigh out before you cube out

Not if it's canned marshmallows.

I get the denting and the rolling, which alone are pretty valid.

I'm not entirely sold on the stacking yet. Why would a round can hold vertical weight better than a square can?

 

[James86004]

I'm not entirely sold on the stacking yet. Why would a round can hold vertical weight better than a square can?

The round shape is a lot more resistant to buckling.

Also, the round shape uses less material to enclose a given volume.

 

[Mr. Leary]

Not if it's canned marshmallows.

I get the denting and the rolling, which alone are pretty valid.

I'm not entirely sold on the stacking yet. Why would a round can hold vertical weight better than a square can?

Its not just stacking. The flat surface will buckle if hit from the side. The round can will just dent. Most canned goods are packed in solution, thus, weight a little less than water.

 

[007]

And really, that's all you need to stock.

Nice!

 

[paulj]

Corned beef is another one that often comes in a rectangular can, though some brands (e.g. Ox and Palm) are in round. Canned fish (sardines, sauries, eel, etc) also come in custom shapes.

Tetra Pak is a brand of cardboard and foil 'can' that is rectangular. Soy and rice milk often comes in this packaging. Tomato sauce and coconut milk also come to mind.

Then there are 'soft' cans, the boil-in-a-bag Indian meals.

 

[wcdu]

Awesome, exactly what I was thinking. Is this list great or what?

wcdu

 

[bobDog]

Gee I thought it was cause the round cans take up more space thus looking like you get more stuff. Like getting 2/3s full boxes...well kinda.
the structural thing makes sense tho.

 

[rusty_tlc]

My guess is volume to surface area, as James said.

 

[Desert Dan]

Sardines?

 

[paulj]

Pluses for round cans:
- maximum volume / surface area means least material cost for the packaging
- ease of manufacture. Cans are often assembled from sheet metal right on the canning line. The round shape is easy to roll. Rims are crimped on.
- standardized sizes
- ease of opening. Some can openers have problems with the sharper corners of sardine cans etc. Span and cornedbeef either have pop tops or tear strips.
- storage space was rarely a premium.
- if you need to maximize packing efficiency, choose larger cans (such as #10 commercial size).

Have you ever opened a #10 can with a counter top opener? The kind with a tooth you jam into the lid, and then turn a crank to rotate the can? Definitely works better with a smooth round can.